As more advanced computer systems make it possible to work with very complex information collections and control options, limited display screen area becomes increasingly inadequate for presenting this information to users.
Modern systems attempt to provide various solutions to this problem. For example, windowing systems divide a computer screen into multiple areas displayed in tiled or overlapping arrangements resembling arrangements of sheets of paper of various sizes on a desktop. Since at least a small part of each window is not hidden by other windows that appear to lie on top of it, a computer user is reminded of the information displayed on the background windows, and he/she can access this information by bringing a background window to the foreground by positioning a cursor on any unobscured point in the desired window and then selecting the window by means of a peripheral device, such as a mouse. Although this method increases the amount of data which is readily available to a user, only a limited number of windows can be open simultaneously. Furthermore, the current windowing style forces one, so to speak, to `live out of boxes`, since the objects that one needs to access are concealed until the logical `boxes`, which contain these objects, are explicitly opened. This deprives a system user of the equivalent of `peripheral vision`, which plays an essential role in daily life.
A commonly employed method of exposing a user to a variety of control functions is by using a menu. A menu presents a user with an array of symbolically represented choices. Usually, when a user selects one of the choices, a list of subsidiary choices is displayed. These secondary choices may, in turn, cause the display of another level of menu choices, so that a sequence of choices of any depth can be provided for a complex computer application. Typically, menus of low level choices are displayed only when mutually dependent successive higher level choices are made. Since all the choices are displayed in identical or comparable size, they take up substantial screen areas and, therefore, these displays of choices are removed once a complete sequence of choices has been made, thereby depriving a system user of any continuing reminder of how a similar sequence of choices can be made again.
Another technique for displaying menus of command options is to continuously present a panel of choices in a designated screen area. To access additional options, a user can interactively replace a currently displayed panel by the next one in sequence. By constantly changing the menus displayed on the screen, a user is frequently confused about the location and availability of a desired operation. In addition, the compressed representations of options used to save display space are often hard to understand, devoid of immediately available documentation, and bewildering to all but the most experienced system users.
Often, a computer requests a user to supply information that goes beyond a simple functional selection. For example, a user may have to supply the name of a file or the value of a numerical parameter. Where a response to a computer generated inquiry is required, a common practice is to display a rectangular `dialogue box` where a user can type in the required input. Because the dialogue box area obscures part of the display area, a user must remove the dialogue box area from the screen by explicitly "closing" it after the required information is entered. Those repeated open/close operations are visually jarring and time-consuming.
Typically, text and graphical files are displayed by "scrolling" the display area, i.e. moving the displayed material "left/right" or "up/down" until a desired line of text or a graphical detail comes into view. A difficulty with this technique is that the number of items that can be displayed simultaneously is severely limited. Since items that are not scrolled into the field of view are entirely invisible, a user, searching for a particular item in a lengthy file, may easily become confused about the direction of the scroll, even when the desired item is only a single line away from the visible portion of the file. The uncertainty that results from the traditional scroll reduces working efficiency of the users of computer systems.
A user of a computer system frequently deals with hierarchical information structures that are organized as a decision tree. As indicated, a typical menu driven system that provides a wide variety of capabilities necessarily includes several levels of menus. Since menu options at the top level do not suggest the options at the low levels, a user needs extensive training to use such systems, or he has to continuously refer to the manuals. Another example of a hierarchical information structure is a directory of files provided by a typical operating system. It usually contains a root directory, which contains files and/or pointers to sub-directories, and each sub-directory also contains files and/or pointers to lower-level sub-directories. Usually, thousands of files can be stored in this fashion. Thus, to access a desired file, a user has to travel up and down through levels of sub-directories relatively blindly. To guide a user who navigates from one menu or sub-directory to another, hierarchical structures can be represented graphically, as a tree. However, such interfaces are still confusing because for a large hierarchy, a graphical representation occupies multiple display screens. The directories, menus, and scrollable displays are even less adequate for presenting diversified data collections that cannot be easily described by a well structured hierarchy.
The computer science community realized that the restricted size of the computer screen detracted from efficient utilization of computers. Several attempts have been made to address this problem by changing the working environment of a computer system user. See A. Bolt, "Spatial Data-Management", MIT, 1979. The researchers at MIT attempted to improve efficiency of user access to information by developing a media room which comprises a wall-sized display screen, two small television monitors, eight loudspeakers, two "joysticks," and two touch-sensitive pads. In the "Data Management" system disclosed in the Bolt article, all the data available to a user is arranged on a single plane, which is displayed in its entirety on the television monitors. Additionally, a smaller portion of the same plane is displayed on the large display screen. The portion of information displayed on the large screen is indicated by a rectangle on the television screen. A user thus has the capability of displaying different portions of the single information plane at several different sizes on the large screen.
The Bolt paper does not teach a commercially useful computer user-interface which can be employed by a wide variety of systems and applications. Although a zooming capability for data management is proposed, the Bolt paper does not address the issue of providing such a capability efficiently using a generic workstation rather than a complicated collection of equipment. Furthermore, for efficient commercial use, an application independent interface is required. However, it can be inferred from the discussion in Bolt that, in order to employ the capabilities provided by the system, the applications have to be implemented specifically for the Data-Management system. Furthermore, the Data-Management system provides an interface for accessing information, but it does not appear to provide an interface for interactive entry and edit of new data. Also, the Data-Management system cannot be used to replace conventional menus, text editors, and other commercially available user interfaces, which use general purpose terminals as a display medium.
Currently available interfaces, which often fail to adequately present to a user commands and information provided by a computer system, do not address the inherent limitation of restricted computer screen size. These interfaces substantially limit the productivity of system users by forcing them into repeated and time-consuming searches of options, menus and the like. Furthermore, the searches are frequently performed without sufficient computer guidance, since not enough information can be accommodated on a limited screen area, and since the information appears and disappears with distracting suddenness. Since the variety and amount of information and control options available to users of computer systems is steadily and rapidly increasing, the limitations of the existing user interfaces will form an increasingly serious impediment to effective system use.